A technology is known which provides a valve overlap period by controlling a variable valve mechanism and increases the amount of fresh air in a cylinder by scavenging gas remaining in the cylinder to an exhaust passage utilizing a differential pressure between an intake pressure and an exhaust pressure during this valve overlap period.
For example, JP2006-283636A discloses a technology which obtains a scavenging effect by controlling a throttle valve opening to make an intake pressure higher than an exhaust pressure during a valve overlap period.